Telephony



F. M. SLOUGH TELEPHONY 2 Sheets-Sheet l INVEZVTOR Filed Aug. 5, 1917 Dec. 392% 1,519,271

F. M. SLOUGH TELEPHONY INVENTOR W-w 3M Patented Dec, 16, 1924.

UNlTED STATES PATENT EFEQE.

FRANK l'vI. SLOUGH, OF ROCHESTER, NEW YORK, ASSIGNQR TO THE STRGMBEBGr-CARL- SON TELEPHONE MANUFACTURING COMPANY, OF ROCHESTER, NEW YORK, A COR- PORATION 011 NEW YORK.

TELEIPHONY.

Application filed August 3, 1917.

To all whom may concern:

Be it known that I, FRANK M. SLOUGH, a citinen of the United States, residing at lochester, in the county of lilonroe and State of New York, have invented certain new and useful Improvements in Telephony, of which the following is a specification, reference being had therein to the accompanying drawings.

An object o't my invention is to provide n eans whereby an A operator may select and apply any desired ringing current or ringing combination at a B position, the same as at her own position, without the it operator being required to do anything except to put up and take down the desired connection. The Jr operator also supervises both at her own and the 13 end of the trunk, and signals the B operator for disconnection when she finally removes her plug from the trunk jack.

It is also an object of my invention to accomplish the aforesaid object without requiring the manipulation of any additional key or selective apparatus by the A operator than would be the case were the A operator selectively signaling a party line subscriber whose line terminates at a jack at her own switchboard.

It has been the common practice in trunking calls between exchanges for the B operator to select the current or combination of circuits necessary to call wanted. subscriber it he be on a party line. lileans have been devised to supervise the connection, and meai'is have also been devised to enable an it operator to select the current to call a party line subscriber at a distant switchboard through. a trunk line by the use of a special key which was required to be tapped by the A. operator in order to send pulsations of current over the trunk line for the purpose of selecting the ringing current to be applied to the called line. This last arrangement is very unsatisfactory as it requires additional time to be consumed by the operator in establishing a connection, and is therefore uncommercial, and so far I am aware has never been used in a working tele phone exchange since traffic requirements call more and more for additional speed in operating both at the A and at the B switchboards.

Serial No. 184,252

Another desired traflic condition which was not met in the previous arrangement above mentioned and which is satisfied in the present invention, is that the operate of the exchange in order to best perform their work should establish all kinds of connections in as nearly as possibl the same way. L

Specifically stated, and referring to a particular system of harmonic selection, in the system of my invention 1 preferably place set of slep-by-step relays at the B exchange, controlling the circuits of tour generators, each adapted to furnish current suitable for ringing the bell at a particular station and no other. Any one of four stations on a line may be called by selecting and connecting the proper generator of this set to that line.

I have illustrated a use of my invention in connection with the ordinary multiparty automatic ringing system of the art at the A operators switchboard. This is a preferred embodiment of my invention. At the El operators switchboard I so construct the interrupters associated with each of the ringing generators of the exchange so as to have additional contact making segments, the said segments being operative duri the so called silent interval of a ringing period to send current impulses over the trunk line, these current impulses being operative to selectively operate the step-bystep relays above mentioned, to select the particular ringing generator at the B operate is switchboard which is capable of signaling the desired party on. the called line, and which generator corresponds to the selective properties of the generator at the A op erators switchboard in whose circuit the selecting segments are placed. These additional segments placed on the ordinary ringing interrupter have no effect on the automatic. ringing system on calls local to the A switchboard, the ringing mechanism bein operative in the usual way on such calls.

My invention is not limited to an automatic ringing system or to manual switchboard systems, but may obviously be applied without alteration to automatic and semi-automatic systems, or to manual systems not employing so-called automatic ringing mechanism. The most t'requent implication will be to branch exchange work, or what we may call clearing house systems, wherein a main central ofiice is provided with manually operated switchboard apparatus, and the branch exchanges i are equipped with apparatus adapted to be controlled through trunk lines from the main office. i

Other objects of my invention and the invention itself will be better understood from the description of the same which follows, reference being had to the two sheets of drawing forming a part of this specification and illustrating a preferred embodiment of my invention.

1 shows the apparatus at the A operators svitchboard consisting ct two lines L and L extending from substations to the exchange, and terminating thereat in jacks J and J On the line L the substation. SL is connected, and on the line L a plurality of substations s s s and 8 are connected. The line L is a party line containing tour substations, the bells of which are understood to be of the harmonic selective type, that is, they are each tuned to respond to alternating currents of a particular frequency; each being differently tuned with regards to frequency. On each of the lines the usual line and cut-oil relays are shown connected in a common manner.

A cord circuit is also shown in Fig. 1 for the purpose of interconnecting telephone lines such as lines L and L and is also adaptable to connect one of the lines to a trunk circuit T a jack terminal of which is illustrated in Fig.'1at J The link circuit C terminates in plugs P and P and these plugs are adapted'to cooperate with the diiferent line and trunk jacks to interconnect any two of the same. Harmonic ringing generators are illustrated at G G G and G and are driven at such a rate of speed to generate each a particular frequency of alternating current adapted to operate a particular one of the four lines on the party line connected to the exchange.

the line L Interrupters I 1 I and L of special construction to be more fully described later are connected in the circuit of the ringing generators just mentioned so that during the ringing period the ringing of the bells may not be continuously intermittent, there being a short ringing interval which may be of one second duration, and a long silent interval which may be of live seconds duration; these being time values commonly employed in commercial systems.

The cord circuit C- of Fig. 1 contains the usual supervisory relays, a and a being the answering and calling supervisory relays respectively and also contains the usual local circuit supervisory relays a" and r zulapted to cooperate with the answering and calling supervisory relays to control the ordinary supervisory signals of. the cord circuit.

The relays r and a also control the automatic ringing circuit in the usual manner which will be later described. Automatic ringing relays are also shown in this cord circuit consisting of the trip relay 2. and the ringing relay T the latter being for the purpose of connecting the ringing generators to the telephone line to signal the called-for station thereof; and the trip relay being for the purpose ofdissocia-ting the said generators and the said substations, and to restore the telephonic connection between the calling and the called-for line, this being the'common practice in the art.

I also show in the cord circuit a listening key 1: adapted to connect an operators telephone set 0 to the cord circuit whereby the operator may converse with the connected subscribers at will. I also show in connection with the cord circuit C a plurality or party line ringing keys K K 'Kg and I'L connected in the usual manner between the party line generators and the trip relay 2? and adapted by their manual operation to connect a particular one of: thegenerators to the ringing circuit to signal a desired station on the connected called party line.

So far, with the exception of the noted special construction of the interrupters associated with the ringing generators, the description is that of the ordinary telephone system of the art.

The trunk circuit T terminating in a jack J in Fig. l is extended by limbs ,1 and 2 to the circuits of Fig. 2. which figure shows the trunk circuit apparatus at the B switchboard, this apparatus consisting in part of the well-known trunk circuit apparatus of the art. and in part of special apparatus provided for the purpose of illustrating an embodiment of my invention. The trunk circuit is shown as terminating atthe B board in a plug P which is adapted to make connection with a jack 5 of a line L It will be understood that both the cord circuit C of Fig. 1 and the trunk circuit T of Fig. 2 is adapted to make connection with any of a plurality of telephone lines only enough of which are illustrated in the drawings to enable the invention to be properly described.

The line L of Fig. 2 is shown extending from a plurality of stations 8... s s and 5., by line conductors 3 and 4 to the B switchboard terminating in the jack J andat the B switchboard there is shown the line relay and the cut-of? relay 6 which are the ordinary line and cut-off relays commonly used with common battery telephone lines. The substations s 8;, a and s have telephone bells b b b and Z2 each of the harmonic type and adapted to be operated trunk circuit proper contaii by alternating current of a frequency corresponding to the spe ial tuning of the particular bell.

Ringing generators. are also arranged at the B board and adapted to be connected in circuit with the substation bells. Interrupters of the ordinary pattern 1 I I and I are also associated with the said ringing generators to break up the ringing period into silent and ringing intervals. Generator selecting relays 7, 8, 9, 10, 11, 12, 13 and 14 are also provided to select the proper ringing generator to ring the particular bell belonging to the called-for station. The s the usual auto matic ringing relay 7",, and ringing trip rclay t supervisory relay 15, third strand local circuit relay 16, trunk line relay l7, and in addition the trunk circuit contains additional relays l8, 19, 20, 21, Q2, 23 and 24 whose functions will later be described.

Referring again to Fig. l. the interrupters I 1 and I each have a ringing segment 2: to which is connected the associated ringing enerator (l. Cr, G. or G as the case ma he. The ground pole of battery is connected to the other segment of each of the. interrupters, and in the ordin ry construction of such interrupters in the a t, this last-named ground segment is tin-broken, that is, its surface is continuously conductivethrougln out its entire length. Associated with each of the interrupters is a brush 6 adapted to contact with the rotating inteirupters, and

' thus to make contact with the outer surface of the revolving interrupter segments.

In the embodiment of my invention illustrated. I interrupt the conducting surface of the ground segment of certain of the 'interrupters and divide this conducting surface into parts, each interrupter being differently divided in this way for the selee-ting function to be later described. The first interrupter l', I provide with the ringing segment '0 as before noted, and considering that the interrupters revolve elocle wise the brush a will contact with this ringing segment and immediately following thereafter an insulating segment i, will pass under the brush, the insulating segment be ing a very narrow segm nt and will pass rapidly under the brush. The rotation con tinuing, contact will now be made with the ground connected conducting segment of (Z with which it will make contact for a relatively long interval until a second short insulating segment 2', is encountered which rapidly passes under the brush Z), the brush will immediately thereafter make contact with the ringing segment Thus when the generator G is operative there will be a i of circuit changes performed by the upter 1 during one revolution thereof wasting of a second ringing interval. a if; second insulating ".icerval. a 4.8 ground interval, and a insulating interval malting a. cycle of 6 seconds total duration.

The second interrupter I is similarly constructed except that following the like insulating segment 2' there will be a short ground connected conducting segment (Z Then another short insulating segment 5,, followed by the main ground connected conducting segment (Z corresponding to the smaller segment (Z of interrupter T the balance of the interrupter being similarly constructed to the similar parts of the interrupter T The interrupter I is the same as the interrupter 1 except that an additional insulating segment 2; is rovided on the surface of the segment (Z a short distance from the insulating segment 2' The interrupter I is constructed like the other interrupters except that while an additional insulaz'iing segment is interposed in the conducting segment (Z, the insulating segments '5 i, and of the interrupter I, being spaced an equal distance from each other and the width of the insulating segment being approximately the same as the width of the conducting surface between them and so proportioned. that it will take each one of the insulating segments approximately of a second to pass under the brush is associated with the interrupter. These proportions are assumed to be the same for the different interrupters and may be varied if desired, the values given being those which I have found to be well suited to the purpose.

As above described it will be seen that the interrupters are much alike, being only different in the number of the short insulating segments interposed on the surface of the ground connected conducting segment (Z thereof.

The selecting apparatus of Fig. 2 adapted to cooperate with the interrupters l l 1, and L to select a ringing generator at the B board to be applied to the called-for line L consists of certain relay mechanism which will now be briefly discussed.

At the top of the figure I show a group of relays in pairs, there being four like pairs of relays as follows :-7-8. 9 10, 11-42, l3l; each of the aforesaid pairs serving when operated to select a particular ringing generator to be applied to the called-for line, the particular generator to be applied depending upon the number of pairs of these relays operated. These pairs of relays are operated in sequence one after the other by intermittently made contacts in their err-- ergizing circuit which is extended to each of the relays successively as they are operated. The controlling contacts for operating these relays are primarily the contacts of the interrupters 1,. 1 lb, and at the A switchboard which intern 'ttently ca itthe operation of the trunk relay 17, causing its contacts to be intermittently operated and in turn intermittently break and make the contacts 25 of the relay 2() by the inter inittent operation of the relay 20 under the control of the relay 1?, and the contacts are placed in the energizing circuit for the pairs of selecting relays above mentioned and control the operation or the same. Other relays 23, 24, 21, 22, 19 and 18 are auxiliary controlling relays whose functions will be better understood vtroin the description of the operation of the system which will follow 1-- The relay 18 is of what is known as the drop relay type. This relay has a condenser 7.: included in its circuit so that it is unatfected by direct current, the condenser being opaque to the flow of direct current, but can be operated by alternating current passing through its winding and through the condenser, the said alternating current causing it to attract its armature 26 to which is attached latch lever 21'' which will be lifted to a-llcw the drop, shutter 28 to tall and make contact with the contact piece 29. Such a drop relay is illustrated in the issued 'lilblll; to this applicant 909,435, patented act. 6, 1908 for a Self-restoring drop relay so that for a better understanding of the operation of such a relay and the mechanical interlocking of certain of the parts, reference can be had to the disclosure of the above patent. During the attraction of the armature 26, contacts 30 will be maintained broken and will be closed again at the end of the ringing periodcausing the operation of the relay 19,, which will then be operatively included in the circuit which serially includes both the contacts 30 and the contacts 2829 closed.

Having thus briefly described the apparatus employed in the above embodiment of my invention, 1, will now describe the operation of the same in the embodiment illustrated.

Assuming it is desired to make a call from the substation s, on the line L to the substation 3 on the line L these lines both terminating in the same exchange at the Aswitchboard, the subscriber will operate the switchhook of the substation 8 and close the contacts 310 and complete a circuit including the line relay 31 of the line operating it, and causing it to close its contacts 32 to operate the line lamp 83 in the usual manner. The operator observing the lamp will answer-the call by inserting the plug P, in the jack J and operate the listening key K to connect her telephone set 0 to the talking conductors of the line. The cut-oft relay 34L will be operated over a circuit including battery and winding of the relay 1, of the cord circuit, and in the usual way operating also the relay T The supervisory relay a will also be operated from the source of current B included in circuit with its windings which are connected to the talking strands of the line 35 and 36 by means of the talking strands of the cord circuit 3'? and 38 through cooperating contacts of the plug and jack switch P J the circuit of the relay a being completed by contacts 31 of the calling substation switchhook. The answering supervisory lamp 239 which would otherwise be lighted by the closure of contacts 40 of the relay a, will be retired by the opening of the contacts 4-1 of the relay a. The closure of contacts 4-2 of the relay (4 conditions in part the circuit of the automatic ringing relay 2", tor operation. The operator upon learning the number of the called-tor line from the calling subscriber, and assuming that it is the line L that is called, will insert the plug l into the jack J making connection thereby between the cord circuit C and the circuitot' the line L and'will cause the relays 1 and 43 to be operated, the relay 43 being the ordinary cut-cit relay of the line, and the relay 1%, being the ordinary third strand local circuit supervisory relay of the cord circuit, these two relays being operated in series when the plug and jack con nection was made in the usual manner. The

cut-off relay a3, of the line L, and also the cut-oil relay 34: of the line L are the usual cut-off relays of the art and perform their functions in the usual way.

In addition to learning the number of the line called for, the operator will have learned frorn the calling subscriber which party line subscriber is wanted on the calledfor line. Assuming that it is a particular one of the subscribers having substation telephone sets s s 8 or a on the line L the operatorwill now depress that one of; the ringing keys K K K, or K corresponding to the particular party of the line desired, and the depressal ot the particular key will cause its contacts to close including in the ringing circuit a particular generator G G G or Associated with these generators are four interrupters, one for'each oi? the generators, the interrupters being L, 1 and 1 respectively.

The construction otthese interrupters has been previously described as having a ring ing segment separated from the balance of the interrupter disc by an insulating segment on either side of the ringing segment, the balance of the conducting poi-- tion of the disc being connected to the ground pole of battery. And it has been previously described how veryshort insulating pieces are placed on portions of the ground connected segment, the number of insulating pieces being different in different interrupters. These insulating pieces are very narrow and have no apparent effect in the operation of the system when connecting two telephone lines terminating in the A switchboard in the ordinary course of making such a connection by means of the cord circuit G outside of the usual effect to be had by the usual. interrupter of the art.

it the time one of the ringing keys are depressed as before mentioned a pair ot contacts let are also closed, these contacts being common to the group of keys. The closure of these contacts will cause the operation of the ringing relay 73,, the circuit being traced as tollows:-1"rom the ground pole of battery, the contacts *l-fl, the wind ing of the relay 2;, the now closed contacts 4-2 of the relay a, the normally closed contacts l5 of the relay 0, and the now closed conta 4:6 ot' the now operated relay r circuit conductor leading to the negative pole of battery l3, this battery being in cluded in the circuit and causes the operation of the relay 2",. This relay being operated it will remain operated regardless of the opening of the. contacts occurring when the operator releases the ringii' key because of the l'iolding contacts #28 w are now closed by the operation ot the controlling relay 73,. Th holding contacts complete locking circuit to ground independent of the initiating circuit includ ing the contacts The ringing of the called-tor subscriber will. now be traced from the negative pole of battery, the resistance coil i9, now closed contacts of the relay r,,, the cooperating ring contacts of the plug and jack switch P J line .-ouductor 51 of the *alled line L the condenser and ringer coils of the called-tor substation on the line L circuit conductor 52 of the line, cooperating tip contacts of the plug and jack switch P J now closed contacts 51 or the relay r the winding ot' the trip relay f, circuit conductor 51-) the now closed contacts of the depressed ringing key K K K, or li and the circuit conductor leading to the particular brush 7/, resting on the surface. of the particular interrupter associated with the partirular generator selected by the operation the ringing key; the circuit being completed from the brush 6 through the said interrupter and thence alternately through the ringing generator to ground, and through the scgn'ient (Z of the interrupter to ground.

It will be seen that in addition to the circuit being completed for the flow of ringing current from the generator that it is at all times conditioned for the flow of direct current from the negative pole of battery to the ground pole thereof, and as soon as the called-for subscriber hearing his bell responds thereto by taking his receiver from the hook, the contacts of the said hook will be closed completing a circuit for the flow of direct current over the line and including the winding of the trip relay t which will thereupon be operated whether the act of the subscriber is performed during the ringing period, that is, if the segment 1) when the operating interrupter is under its brush 7), or whether on the so-called silent interval when the ground connected segment (Z is passing under the brush 6. The insulating pieces 2' 2', and one or all of them as the case may be, located upon the surface of the operating interrtupter being operative to interrupt the flow of direct current for too short intervals to produce any a preciable effect upon the operation of the relay If, the relay 2? being what is known as a slow releasing relay and which relay will not flutter for such quick interruptions of current as these insulating pieces would produce. The trip relay being operated will close its contacts 54 and short circuit the relay r which will be released opening the locking circuit at the contacts 44, and the ringing system will thereupon be restored. to normal re-establishing the talking circuitby the closure of the contacts 55 and 56 of the relay r The supervisory lamp 5? which has: been previously lighted over a circuit including now closed contacts 58 of the relay 1", and normally closed contacts 59 of the relay 0 will now be extinguished by the openin of the contacts 59 of the relay 0, advising the operator the called-tor subscriber has answered the call.

The above assumption has been included for the purpose of explaining how in applicants structure the added insulating pieces on the interrupters fail to have any harmful effect in the usual operation of the ringing system of the cord circuit C when the cord circuit C is being used to establish connection between two A board subscribers.

lVe will assume that instead of the line L being the called-for line, that the calledfor line is the line L, terminating in a branch oflice at which is located a B operators switchboard, and at which switchboard the trunk circuit '1 terminates in a plug P the other end ot the trunk circuit terminating at the A switchboard in a jack J In such a case the A operator upon learning the number of the called-for line and the party line designation for the particular party on the line desired, will depress an order wire key not shown in the drawings and over an order wire not shown. but the connection of which is well understood in the art, advise the B operator of the number of the line with which connection is desired, and the B operator having a number of trunk lines, such as T available for the connection will reply to the A operator advising her in the usual way that it is the trunk circuit T that is to be used for the connection, it being common practice to designate the trunk lines by numerals,

Ii 72 O Upon receiving the trunk line assignment the A operator will insert the plug P of the cord circuit G into the jack J of the trunk line, and the B operator upon receiving the assignment of the called-for line will insert the plug P into the jack J 4 of the called-for line L So far the establishing of this connection from the A switchboard and from the C cord circuit to the called-for line does not differ from the usual practice. The A operator however, instead of having advised the B operator of the party line station desired only advises the B operator or the line itself that is desired, and in order to provide for the proper partys telephone on the line being selectively signaled will now depress the particular ringing key K K K or K corresponding to the particular party on the line to be called, thus applying selective ringing current intermittently to the trunk line T, just as ringing current was applied intermittently to the called-for line L as has been previously described. Thus, the A. operator upon inaking different connections operates her apparatus in much the same way providing uniformity of op era-tion.

At the B switchboard is located drop relay 18, which has been previously described, and this relay is the first apparatus of the trunk line at the B board operated under the control of the A board apparatus. However, prior to the operation of this relay, the relay 16 which is the third strand local circuit relay of the trunk circuit at the B board must be operated. This relay will be operated over a circuit including the cut-off relay 6 of the calledfor line L and the-circuit is traced from the ground pole of battery through the winding of the cut-off relay 6,. cooperating contacts of the plug and jack switch P -J circuit conductor 60, the winding of the relay 16 to the negative pole of battery. This circuit being closed battery will flow over the same operating the cut-off relay which performs itsusual function of dissociating the line relay from the line,v and the relay 16 will also be operated attracting its armatures and switching various circuits.

The contacts 61 of the relay 16- will be closed completing a circuit for the opera tion of the relay 21, this circuit being traced as follows :-;tronr the ground pole of battery, now closed contacts 61 of the relay 16, circuit conductor 62, the winding of the relay 21 to the negative pole of battery; This relay 21 will be operated operating in turn the slow releasing relay 22 over a circuit traced as follows: from the ground pole oi battery, the now closed contacts 3 of the relay 21, the winding of the slow releasing relay 22 to the negative pole of battery. This slow releasing relay being opeat'ed will close its contacts 66%, but the closing of these contacts will not have any function at the present time, but will have a function when the connection is taken down as will be later described. The contacts 65 of the relay 16 being closed will condition a circuit for the ringing relay r but this relay 7; is kept from operating at the present time by other contacts which must first be operated. The contacts 66 of the relay 16 will now be closed completing a circuit including the source of current B and the trunk signal lamp 6?, this circuit being traced as "iolloii's: from the negative pole of battery E the si n'al lam 67, the now closed con tacts 66 or the relay 16, circuit conductor 68, the normally closed contacts 69 of the relay 20, circuit conductor 70 leading to the ground pole of battery. Thus current flowing over will operate the signal lainp 67 which will display a signal indicating to the B operator that connection had been completed at the B end of the trunk line only. Thenever connection is completed at the A switchboard the relay 26' will be operated will be later seen opening thecontaets 69 and extinguishing the signal lan'ip 67, indicating to the B operator that connection had been made at both encs or the trunk line. The contacts 71 of the relay 16 will be broken when the relay 16 is operated for a signaling function to be later described in connection with the description of the operation of the signal lanip 67. Contacts 72 of the relay 16 will now also be closed completing a circuit for the drop relay 18 whenever the A operator has niade connection with the trunk line T by inserting the plug P of the cord circuit G into the jack J of the trunk line T and depressed the proper ringing key correspond ing to the particular party line station desired on the line L This the A operator will do soon as she has made connection with the trunk line and we will first consider that she depresses the key K locking the contacts thereof in closed circuit and closing momentarily the contacts coininon to the group of selective keys K Y K and li The closing oi the contacts will operate the ringing rclaly ca'us' it to at tract its armatures, which when attracted will switch circuits in a manner just as was the case when connection was made to the line L, terminating in a jack J at the A s' ritchboard, and which has been p'reriously described" and this part of the description need not here be repeated; suilicient to say that the ringing relay r w'vi-l-l be ope'i el y locked by its locking contacts 48, and} that the contacts 51 and 50 when closed will: conne'ct the signaling generator circuits through to the terminals of the trunk line T,battery being superposed over the ringi-i'ig circuit in addition: to the intermittent sunsets-e i l associated brush Z to the terminals oi line conductors l and 2 of the trunk line i. l ntil ringing current is thus applied to the trunk line conchictors the drop rela 18, cannot be operated since the condenser Z: i included in its circuit at the B board and the condenser being opaque to the flow of direct current, direct current flowing over the circuit through the interrupter 1,, will not influence the drop re. a v to operate, but when the ringing interoccurs due to the a j of the in 1' l as has been described, this ring;-

c'nrrent being alternating in character, ause the magnet the drop relay 18 to opc attx the circuit causing" this operation 4f traced as follows: trou'i the ground pole of battery at the A switchboard, the

orator (l the s gment ii of the interruotcr the brush Z, thereof, circuit conductor To, the now closed contacts of the her K... circuit conductor 53. the winding of the t relay 7?. the contacts 51 of the relay 1 tip contact ot" the circuit conductm' 76, the

, cirplug: P he tip spring of the jack 5..

cuit conduct-or of trunk line leading to the B switzuiboard, the winding 77 ot r peating coil at the R switchboard, cir

cuit conductor 78, the now closed contacts T2 of the relay l6, circuit conductor 79, the coiulenser 7c. the riuding oi? the relay l circuit conductor 80, circuit conductor 1 the iornially closed contacts 82 of the rel 19. circuit C(HM'lIHTtMT 83, the winding of the rep ating: coil, the trunk line conductor leading to the .Qt" switchboard. the ring};

. spring ot tue pic-.1 J located at the M switchboard. the ring contact of the plug i w l now closed contacts .34) otthe relay t 1 resistance coil l-S) to the negative pole of bati'ilternating current from the circuit will fl over this circuit and cause operation of the relay 18. y 18 beingoperated orer tie (,ircuit just described will attract its armature .10, which. will raise the lever 27 and let all the sluitte" thereof.

close contacts The reh The falling oil this shut-t er will ot' the drop relay but the contacts in circuit therewith will remain open thl'OllgllOllt the ringing interval since the armature 52o during this time remains close to the core of the relay 18, and there tore keeps hrol-;cn the contacts 30 for the entire interval. At the end of the ringing interval however, the contacts 30 will he rcestablished, but the contacts 2829 will re in in closed and a circuit will. therefore he pleted for the relay 19, this circuit heing traced as follows: from the ground pole of battery, he armature the contacts 3-0 and the cont 5 2S-29 oi the relay l8. circuit conductor the winding, of the relay 19 to the negit. e pole of battery.

la te current will *low over this circuit inc the winding 0*? t1 ,e e at d will operate the re. p tract its arinatures sn described. The

COZLIZMWS relay 16.

Contacts 82 ot the r A switchboard through the windi.. 7. and 84 of the repeating coil at the B switchboard, and through conductors 85, 86 and 81, the now made contacts 74 of the relay 19 and conductor 87. The relay 1'? being now placed in circuit with the trunk line wires will be ope "ative whenever current is sent over the trunk line following the. ringing period as will be later described.

The contacts 88 of the relay 1?) will now be closed connecting the negative pole of h;:t tery by means of conductor 89 to certain portions 01"" the circuits of the group of relays 7 to 14*. inclusive, well as. the relays for the abort-named relays, and the c ,ntacts 88 ot the ielay 19 the common ba tery control ling contacts of their circuits. hese ontac i remain made until both the A, and B operators have dis-established the trunk line connection at the two ends of the trunk will be later described.

Now following the ringing interval, the interrupter L, the A switchboard will continue revolving until the hrush 6 contacts with an insulated portion of the interrupter for a moment. it this tune the contacts of the relay 1? are opened and the relay 2 deer.ergized thereto the closing; of the contacts 88 of the relay 1'9 will complete a circuit for the relay 'i'; the circuit being traced fOllWWSZ "from the negative pole of battery, the hat. controlll r contacts 88, the battery supply conductor 89, the winding of the relay 7, the normally made contacts 95 01? the relay 8, circuit conduct 96, the normally made contacts 25 of the relay 20, circuit conductor 97' to the ground pole of battery. The. relay 7 will attract its arlnatmies closing contacts 98 and Contacts 98 will condition a circuit for the operation or the relay 8 whenever the contacts 25 are broken as will be described, the contacts 25 at this time maintaining a short circuit about the winding of the relay 8. The contacts 99 of the relay 7 beingclosed, a circuit is completed for the operation of the relay 23 traced as follows :from the ne ative pole of battery, the closed contacts 88 of the relay 19, common battery conductor 89, the resistance coil 100, the now closed contacts 99 of the relay 7, circuit conductor 101, and the winding of the relay 23 to the ground pole or battery. The relay 23 will therefore be operated attracting its armatures and switching circuits to be later described.

In passing it will be noted that there is a circuit provided to shunt the winding of the relay 23consist-ing of contacts 104, circuit conductor 105, normally opened contacts 106 of the relay 20, and conductor 97 leading to the ground pole of battery. The function of this shunting circuit will be later further described. I

At the time the relay 23 was operated the contacts 102 and 103 were bro-ken, biit the breaking of these contacts at this period of the operation 01 the sy-Ste fi'l performs no function, and the contacts 107 and 108 of the relay 8 in circuit with the aforesaid contacts at this time being opened,

The contacts 109 of the relay 23 being closed will complete a circuit for the operation of the relay 2 1-, the circuit being traced as fo-llows:'fro'm the ground pole of battery, the contacts 109, the winding of the relay 2a, the resistance coil 110, circuit con du'ctor 89, the closed contacts 88 of the relay 1 9 to the negative pole of battery. Current flowing over this circuit will operate the relay 2 1 attracting its armatures and closing contacts 111, 112 and 113. The closure of the contacts 111 and 11:2 will not perform any function at this time due to the coin tinned opened condition of the contacts 107 and 108 in circuit thereof. The closure of the cont-acts 113 however, will provide a locking circuit for the relay 24 to keep this relay operative independent of the operation oi the contacts 109 of the relay 23.

Tu passing it will be noted that a shunt including the contacts 11 1- oi the relay r, and conductors 115 and 116 is placed about the winding of: the relay 2 1, to de-ei'iergiz'e the same; but this shuntwill not now be operative due to the opened condition of the contact-s 111.

The interrupter 1 continuing to revolve will. cause the brush Z) to leave the insulated segment following the ringing segment 0 to contact with a ground connected contacting portion or the segment (Z or the interrupter. Such contact is only made momentarily, but it iso'li suii'icient duration to cause arter to how over the trunk line from the ground connected segment through the brush 6, conductor the contacts of the key K the winding of the trip relay 2 contacts :31 of the relay 03,, conductor 76, the tip of the plug P and the tip of the jacltJ conductor 2 of the trunk line, the winding 7 of the repeating coil, conductor 87, contacts 74 of the relay 19, conductor 81, conductor 86, the low resistance winding 90 of the relay 17, the high resistance winding 91 thereof, conductor 85, repeating coil winding 81, trunk line conductor Z, the sleeve spring of the jack J the sleeve contact or the plug P the contacts 50 of the ringing relay r, at the A switchboard, and the resistance coil 19 to the negative pole of battery,

The momentary flow of battery over the circuit just described will cause a momentary operatioii of the relay 17, causing it to close its contacts momentarily, completing the circuit for the relay from the ground pole of battery, the now closed contacts 92 of the relay 17, circuit conductor 93, the winding 01 the relay 20 to the negative pole of battery. This circuit being closed battery will flow over the same energizing the relay 20, causing it to. attract its armatures, switching circuits to be described.

The contacts 9 1 being closed will at this time perform no additional function. Contacts being opened will remove the short circuit which has been noted as being placed about the winding oi? the relay 8 by these contacts, and therelay 8 will therefore be operative in series with the relay 7, the circuit being traced as followsz-t'rom the groundpole of battery, the now closed contacts 9 8 of the relay 7, the winding of the relay 8, the winding of the relay 7, circuit conductor 89, now closed contacts 88 of the relay 19 to the negative pole of battery.

The relay 8 being operated will attract its four armatures closing contacts 107, 108, 117 and 118, and will open its contacts 95 all for purposes which will be later described.

The closure of the contacts 107 and 108 will not be operative to perform any operative -function at this time since at this time the serially connected contacts 102 and 103 of the relay 23 are in their opened position. The closing of the contacts 107 and 108 however, is for the purpose of conditioning the circuits in which they are included for later operation as "will be later described.

The opening of the contacts 95 and the closing of the contacts 117 is for the purpose of extending the counting relay operating conductor 96 to contacts 95 from their operative connection to the pair of relays 7 and 8 to a similar operative connection to the relays 9 and 10 in a manner which is well understood, the conductor 96 thereby being e:-:- tended by means of conductor 119 to an armature of relay 10. The operation of the contacts 118 conditions the generator G and its associated interrupter I to be connected to the ringing circuit. However, since the A operator has depressed the key K instead of K there will be operated additional counting relays of the chain to again dissociate the ringing generator G trom the ringing circuit before it has been tully connected to the called line as will be later seen.

During the momentary attraction of the relay the shunt circuit which has been previously mentioned as being operative is operable to short the relay momentarily placing a short circuit about the winding of the relay 23; but as is well known a short circuited relay releases its armatures very slowly, and the duration of the operation of the relay 20 is so short that the relay 23 will not have time to release its arniatures before the relay 20 is again in its Lin-operative condition. It will now be easily understood how the various pairs of counting relays 7-8, 0-1.0, 11-12, 13-11 will be operated in sequence by successive nnpulses ott current flowing over the trunk line by the operation of the particular interrupter 1 I 1 or I chosen by the act of the operator depressing her ringing key In the case of the interrupter 1 the operation of which I have been specifically describing, there will be three successive operations of the relay 17 which will close the contacts 92 successively three times, the last impulse of current being a long impulse of current, the contacts 92 on the last impulse will be closed a correspondingly long time. The impulse being relayed by the relay 20 and contacts thereot to the conductor 96, which we will call the impulse conductor, the operation of the successive pairs of counting rebefore mentioned will be initiated by current flowing over this conductor, which conductor will be extended from one pair to the next succeeding pair of relays by the operation ()1 the second relay of each of the pairs. Therefore, by the well-known action of such relays it will be seen how the two short impulses and the long impulse of current will cause to operate the relays 7, S, 9, 10. 1.1 and 12 thereby selecting the generator (l, for connection to the ringing circuit at the B switchboard over a circuit which will he later traced,

The ringing relay 1; will. now be operated, :he sai e being at this time operated because the relay 20 is operated for a longer period on this last impulse which is a long impulse of current; the operation of the relay 20 therefore causing the relay 23 to be short circuited, by the contacts 106 of the relay 20, for a suficiently long time to allow the relay to release its armatures closing contacts 103 and 102, and opening contacts 109 thereof. The opening of the contacts 109 will for the moment have no effect upon the serially connected relay 2%, since this relay is tor the time being locked in circuit by its own contacts 113- The closure 01 the contacts 102 however, since the contacts 107 of the relay 8 and the contacts 112 of the relay 2 1 are now closed, complete a circuit for the operation of the relay 9;, this circuit being traced as follows: from the ground pole of battery, the corn tacts 107 of the relay 8, the contacts 102 of the relay 23, contacts 112 of the relay 2 1, the winding of the relay m the resistance coil 120, the now closed contacts of the relay 16, the normally closed contacts 121 of the relay 15, and now closed contacts 88 of the relay 19 to the negative pole of battery. The ringing relay Q will now therefore operate by current flowing over this circuit attracting its armatures and switching circuits later to be described.

The closure of the contacts 103 of the relay 23 will cause the high resistance winding 91 of the relay 17 to be short circuited momentarily for the purpose of operating the trip relay t at tie A switchl'ioard to cause the disconnection of the ringing circuit atthe A switchboard, and to reestablish the talking circuit at the A switchboard in the well-known manner.

In passing it may be said that the high resistance winding of the relay 17 will preferably be made so high so as to have no eltect upon the trip relay t, and the low resistance winding will be made very low so that when the high resistance Winding is short circuited the low winding will allow sutlicient battery current to flow over the circuit to cause immediate'operation of the trip relay which will perform in the usual manner, only short circuiting the ringing relay at the A switchboard and cause it to restore its armatures to normal position.

The shunted circuit for the high resistance Winding 91 of the relay 17 may be traced as follows :-from the conductor 85, the circuit conductor 122, the now closed contacts 111 of the relay 2 1, the now closed normal contacts 108 of the relay 23, the now closed contacts 108 of the relay 8, and circuit conductor 123 to the other side of the winding 91 of the relay 17. The short circuiting ct this high resistance winding will be ol" short duration, preferably only a traction 01 a second, so that the effect. it any, upon the supervisory signal at the A switchboard will be negligible.

The relay n, being operated will cause its contacts 124: to be closed, thereby providing a locking circuit for the relay 11, through these contacts locking the relay i in Opera tion regardless of the controlling contacts initiating the operation just described. The contacts lll of the relay n will also now be closed short oircuiting the winding of the relay 2& and deenergizing thesame slowly. The-relay Qtwilltherefore release its armatures opening the initiating circuit of the relay 7;, and remove the shunt about the high resistance winding 91 of the relay 17.

Contacts 125 and 126 in the talking strands of the trunk circuit at the B board are now broken, and the contacts 127 and 128 in the ringing.- circuit are closed, thereby conipleting the said ringing circuit from the generator G and dissociating interrupter I, fronrtheexchange to the bells of the called line, the saidgenerator.illustrated-being a selective ringing generator, preferably of the harmonic types and ringingcurrent will therefore flow from the said generator over acircuit which will now be-described, ringing: a particular. one o'lti thebells on i the line which-willhe such a bell as'is adjusted to operate inconnection with the particular generator G and stherefore the desired 1 substation onithe called-for linewill be signaledi The ringingvcircuit-canibe traced as follows :-f1"om ground through the generator- G, and the-interrupter 1,, through the lamp-in circuit thereof; the contacts 129 of the relaylQ, circuit conductor 136), normal- 1y: closed contacts 181iotthe relay 1 1, circuit conductor 132, the winding of the trip relay t the now made contacts 1270i the relay T1,, the tip of the-trunk plug,.thei-tip of the trunkajack J the conduct-or tor the called line through the four bell circuits of the four stations on the line, the line conductor 3, the ring-spring of the jacltd the ring jaclcoi' the plug P the now closed-contacts 12S0t the relay and resistance-coil 133 leading to the negative pole of battery. Ringing current passing over this line will pass through the windings ofthe bells on the line, and Y will select that one 01 them i corre sponding to the ringing generator.

lVhe-n the called-for; subscriber responds as by taking the receiver troni the hook-and niaking'a path for directcnrrent across the callediline, the trip relay t lathe-ringing circuit will be operated :by the direct-' current flowing over this circuit in'the usualway, thus short circuitingthe relay- 71, which will release its armatures and restore the contacts associated therewith to normal, inclut'l ing the opening of the contacts 124 which are the locking contacts oftherelaym The talking strands will be reestablished" at the contacts 125and 126 ot' therelay r The supervisory relay 15-will be operated inxthe well-known manner and will keep open. the contacts 121 in thecircuitof the ringing'relay r toprevent reringing. the operatively connected called subscriber, and will close contacts 134 which short circuits the high resistance-winding 91 of the trunk relay 17 5 and in the usual manner thereby provides a comparatively low resistance path tor the fiow'of battery current from the A switchboard through the windings of the supervisory relay 0, thus operating this super visory relay and extinguishing the supervisory signal in the usual manner.

heir the called-for subscriber" has" finished the conversation with the-called-subscriber at the A switchboard hewillretire his telephone from the circuit restoring the supervisory relays at the-l3 and A switchboards to normal, and the-A operator" will 5 thus get the disconnect signal bythe relighting'ofthe signal lamp -57 and will"take plug P t'ronrthe-jack: J which willcause-batterv to be withdrawn from the trunk line T, and will deenergize the trunk relay 17 at the B switchboard, thus restoringit-to normalandin turn the relay 20 to normal, and will light the trunk line lamp 67 by means ci -the contacts 66 otthe relay l6'andcontacts'69 ofthe'relay 20: This will give the disconnect signal to the B operator who-will disestablish the connection at the B switchboard by taking the plug P from the jack J thus restoring the line circuit to normal and the relay 16 to normal which in turn will restore its control circuits to normal, including the circuit ozt the relay 21'. This relay will be deenergized and will'cause the contacts 135' to be again closed completing a path for current from ground to the said contacts 135; the still closed' contacts 64 of the relay 22, circuit conductor 136leading to magnet 137, and from thence to the negative pole oi'battery. Current momentarily flowing over. thiscircuit will energize the restoring magnet 187 which Will restore the drop' relay 18 to its normal position and open the contacts 28-29 thereot and restore. its controlled relay 19 which in turn will restore the circuits controlled thereby to normal. The trunk circuit is now in condition foranother call.

From the above description-it willbe understood'how other iuterrupters andthe interrupter l sending: a different numberof current impulses over the trunk line during the so-called silent. intervalot the ringing current will operate varying numbers ot the counting relays, and thereby include different selective ri ging generators in circuit with the called line atthc trunk switchboard.

Other: features of operationwhich are well understood have not been specifically described, their operatioiii. and functions being apparent.

lVhat I clainris:

1. In a telephone system,thecombination of an A switchboard a Bswitchboard, a. cord circuit at the A switchboard,- a trunk; line circuit leading from the A. sw-itchboardnto the B switchboard, ringing keys at the A switchboard adaptedto select ringing circuits, aplura-lity' ofc-ircuit interrupters. each capable of producing a dii'ierent characteristic series of circuit interruptions, a plurality of ringing generators at the B switchboard adapted to selectively signal telephone substations, a called line at the B switchboard having a plurality of telephone substations with selective ringing means included therein, and electromagnetic means at the B switchboard adapted to selectively associate a particular ringing generator with the called line, means to include one of the said ringing circuits in circuit with the said trunk line, means to include one of the said circuit interrupters in the said ringing circuit, and registration means at the B switchboard operating under the control of the included interrupter to register the character of the series of interruptions produced by the said included interrupter, said electromagnetic means at the B switchboard being under the control of the said registering means.

2. In a telephone system, the combination oi an A switchboard, a B switchboard, a trunk line interconnecting the switch boards, a called line at the B switchboard, selective bells on the called line, selective ringing generators at the B switchboard, electromagnetic means to select a particular one of the said ringing generators; at the B switchboard to ring a particular selective be l on the called line, like ringing generators at the A switchboard adapted to selectively operate selective bells and ringing keys at the It switchboard controlling the connection of any of the last named ringing generators and the trunk line, current impulse contacts and a source of current also adapted to be included in circuit with the said trunk line by the said ringing keys, said contacts controlling the operation of the said electromagnetic means at the ll switchboard.

3. In a telephone system, the combination with a link circuit at a call originating switchboard section, of a link circuit extended from the said switchboard section to a call extending switchboard section, a called line at the last-named switchboard section. containing a plurality of selective telephone signals, selective signal operating means at the last-named switchboard section to 09- erate the said signals, selective electromagnetic means to select a particular one of said si nal operating means to operate a parti one of the said telephone selective signals, like signal operating means at the extending section, a plurality of switching contacts each adapted to include a particular signal opi-zrating means in circuit with the said call extending link circuit, and impulse means likewise included in the circuit of the said switching contacts whereby the said impulse means selectively controls the operation of the said electromagnetic means at the (all extended switchboard section.

4. In a telephone system, the combination of an A switchboard, B switchboard, a plurality of party line ringing keys for the A switchboard, a plurality of selective ringing generators associated therewith, a trunk line interconnecting the switcl'iboards, a called line at the B switchboard, means to interconnect the said trunk line and said called line, a plurality of selective telephone signals on the called line, a plurality 0t ringing generators at the B switchboard adapted to selectively operate the said signals, interrupters at the A switchboard to break the ringing period into ringing and silent intervals, impulse contacts for the said interrupters adapted to be included in circuit with the said trunk line during the said silent interval, and electromagnetic means controlling the selection of the ringing gen erators at the B switchboard under the control of the said impulse contacts at the A switchboard.

In a telephone system, he combination of an A switchboard, a B switchboard, a trunk line terminating in switching terminals at each of the switchboards, a plurality of ringing generators at the A switchboard, means to selectively include one of the said ringing generators in circuit with said switching terminals, a selective key for associating a particular one of the said generators with a pair of the said switching terminals, interrupters tor the said generators adapted to break the ringing period into ringing and silent intervals, contacts operated by the said interrupters during the silent interval, a diile-rent nun1- ber of contacts being so operated for each of the ringing generattws, selectively operated .i'neans at the B switchboard adapted to be selectively controlled by the said contacts, a telephone line at the B switchboard adapted to be associated with the said trunk line by the other pair of switching terminals, said telephone line having a plurality of selective signals thereon, a plurality of selective ringing means at the B switchboard, each adapted to selectively operate the said selective signals on the said telephone line, the said selective operated means controlling the connection of the said selective ringing means to the said switching ternqiim is.

6. in a tele" one system, the combination of an r; viitchboard, a B switchboard, a cord circuit at the A switchboard, a: trunk line circuit leading from the A switchboard to the B switchboard, ringing keys at the A switchboard adapted to control selective ringing circuits, an auto matic ringing relay controlled thereby, a trip relay for the said automatic ringing relay, interrupters included in the said ring in circuits, a plurality of "inging gene-raters at the B switchboard, a called line at the B switchboard, and selective stepby-step means to associate anyone of the said ringing generators with the said"ca lled' line, said selective stepbystep meansbeing under the "control oi' the said interrupter-s.

7 Ina telephone system, the combination of an A SWltOlll'JOttlCl, a B switchboard, a cord circuit at the rh 'sw-itchb'oard', atrunklinecircuit leading from the A switchboard to the B switchboard, ring ing keys at the A switchboardi. adapted to" control selective ringing circuits, an auto-' matic ringing relaycontrolled thereby, a trip relay for the said automatic ringing relay, interrupters included in the said ringing-circuits, a plurality of ringing generators at the B switchboard, acalled' line atthe B switchboard, selective step-bystep;meanstoassociateany one ofthe said ringing generators with the said called line, said selectivestep-.by-step' means being under the control of the said interrupts-rs, andmeans at the B switchboard operating-after a connected"interrupter has completed" a cycle of interruptions to cause the said trip relay to operate the said automatic relay whereby the said automatic ringing relay will dissociate-thesaid ring ing circuitsfrom the said i trunk line:

8. In a telephone system, the combination of an AW'switchboard, a B switchboard, a cord circuit at the A switchboard, a trunk linecir'cuit leading fromithe A switchboardto the B switchboard, ring ing keys at the-Al'switchboard adapted to control selective ringing-circuits, an automatic ringing relay controlled thereby, a trip relay for the said automatic ringing relay, interrupter-sincluded in the said ring-' ing circuits, aplurality of ringing generato-rsat the-B switchboard, a" called line at the B switchboard, selective step-bystep means to associate any one ofthe said ringing generators with the said-called line, said selective ste=p'bystep means being under the control of the'said-interrupters, means at the B switchboard operating after a connected interrupter has completed acycle of interruptions to cause the said trip relayto operate the said automatic relay wherebythe said automatic ringi :3 relay will dissociate the said ringing circuits from the said trunk line, andsup'ervisory signaling means: at each of' th'e switchbbards made operative after the operation oi the saidtrip relay.

9; In a telephone system, thecombination oi an A switchboard, a-B switcl'rboard, a cord circuit" at the A switchboard and a trunkline interconnectingthe said cord with the B switchboard, a ringing citcuit tor the said cord circuit, an automatic ringing means at the iiswitchboard including ringing genera-torsand a source of direct current" for controlling said ringing circuit,- coninrutating contacts adapted to be alternately included 111S21ltl ringing. circuit, step-by-step means at the- B- switchboard adapted to be operated by the saidconnnutatingcontacts, a telephone line at the B switchboard having a plurality oi' selective signals thereon eaclr of said signa-ls being of a type adapted to'be selectively operated byi a particular generator at" the B switchboard said step-bystep meansselecting the particular generator tooperate a desired sig-na-l at the said telephone line,

10. In a telephone system, the combination of a call extending switchboard, a trunking switchboard,- a link circuit at the call extendingswitchboard and a trunkline leading from thesaid call extending switchboard to the trunking switchboard to interconnect the said link circuit and the said trunking switchboard, switch terminals for the trunk circuit at; the trunking: switchboard: to extend the trunk circuit to con nection: with a: called line and a ringing circuit1 associated with thesaid: link circuit, a'plurality of commutators: producing diiferent successive series of circuit interruptions, means to interconnect the said ringcircuit to the said trunk circuit through co-operating terminal contacts of said link circuit: and'said trunk circuit, a switch to include any of said commutators in said ringing; circuit, means to interconnect c0- operating: terminal contacts of said link circu it' and a desired called line, signal'bells on the saidcalled line adapted to be operatively: included in the said ringing. circuit to=ringj the said bells, a. plurality of selectii'e' ringing circuits at the trunking switchboard, sources of current connected thereto, selective switch icontacts adapted to operatively include one of the said" ringing circuits with the trunking switchboard called line to selectively operate asignal bellzon the said-line, saidiselective switching, contactsbeing operated under the controlof azcommutator' included in the ringing? circuit at the call extending switch board to." operatively include. a particular selective signaling circuit at the trunking switchboard. in circuit with the called line, through: said trunk circuit switching ter minals', saidiselected selective ringing circuit corresponding to the particular commutator included in the said link circuit ringing circuit.

11'. In a telephone system, a plurality of groups of telephone lines terminating in switching terminals in aplurality of switching. stations, a trunk line to interconnect telephone lines otitwo ofthe said groups, said trunkline comprising a pair of talking conductors, a plurality of substations-on one of the telephone lines, signals at each of the said substations adapted" to be se-' lectively operated, means to connect one end of the said trunk line to the switching terminals of the said line, switching means at the distant switching station adapted to associate a link circuit at the said station with the other end of the said trunk line, a ringing circuit associated with the said link circuit including a ringing generator, stepby-stcp switching means associated with the end of the trunk line distant from the connected linl-z circuit, a plurality of selective ringing generators, said step-by-step switching means being adapted to variably connect one or another of said selective ringing generators to the circuit of the said line to selectively signal one or another of the sta tions thereon, a. source of current and a circuit breaker included in the ringing circuit associated with the said link circuit, current from the said source being capable of being projected through the said circuit breaker and over the said r'nging circuit and the said trunk line, talking conductors to variably operate the step-by-step switching means whereby said circuit breaker by its variable operation controls the selection of a desired station on the said line.

12. In a signaling system, the combination of a stepby-step mechanism, a plurality of signaling generators one or another of which is adapted to be included in a signaling circuit by the operation of the said step-by-step mechanism, relay controlling means for the said switching mechanism, circuit conductors extending from the said switching mechanism and the said controlling means to a distant impulse sending station, a source of alternating current and a source of direct current at the said station, a commutator at the said station controlling the connection of the said sources of current to the said switching mechanism over the said circuit conductors, the said commutator having contacts adapted to be operated one after the other in periods, one of the said contacts being connected to the alternating current source, a plurality of other contacts being connected to the said direct current source whereby the said commutator causes currenttrom the said source through the said contacts to How over the trunk line and the said switching mechanism in sequence, electromagnetic means associated with the said switching mechanism, controlling means adapted to be operated by the said alternating current source, contacts operated by the said electromagnetic means to make operable the said switching mechanism whereby the said switching mechanism can operate to select any of the said signaling generators until after the connection oi the said alternating source through the said commutator to the said switching mechanism.

-3. In a signaling system, the combination of a step-by-step mechanism, a plurality oi? signaling generators one or another of which is adapted to be included in a signaling circuit by the operation of the said stepby-step mechanisn'i, relay controlling means for the said switching mechanism and the said controlling means to a distant impulse sending station, a source of alternating current and a source of direct current at the said station, a comn'iutator at the said station controlling the connection of the said sources of current to the said switching mechanism over the said circuit conductors, the said commutator having contacts adapted to be operated one after the other in periods, one of the said contacts being con nected to the alternating current source, a plurality of other contacts being connected to the said direct current source whereby the said commutator causes current from the said source through the said contacts to flow over the trunk line and the said switching mechanism in sequence, electromagnetic means associated with the said switching mechanism, controlling means adapted to be operated by the said alternating current source, contacts operated by the said electromagnetic means to make operable the said switching mechanism whereby the said switching mechanism can operate to select any of the said signaling generators until after the connection of the said alternating source through the said commutator to the said switching mechanism, and additional electromagnetic means adapted to be operated by the last impulse of direct current preceding the next succeeding alternating current impulse to operatively lock the said switching mechanism to operatively connect a selected signaling generator to a signaling circuit common to the said generators.

14. In a signaling system, the combination of a step-by-step mechanism, a plurality of signaling generators one or another of which is adapted to be included in a sig naling circuit by the operation of the said step-bystep mechanism, relay controlling means for the said switching mechanism and the said controlling means to a distant impulse sending station, a source of alternating current and a source of direct current at the said station, a commutator at the said station controlling the connection 01 the said sources of current to the said switch ing mechanism over the said circuit conductors, the said commutator having contacts adapted to be operated one after the other in periods, one of the said contacts being connected to the alternating current source, a plurality 01 other contacts being connected to the said direct current source whereby the said commutator causes current from the said source through the said contacts to flow over the trunk line and the said switching mechanism in sequence, electromagneic means associated with the said switching mechanism, controlling means adapted to be operated by thesaid alternating current source, contacts operated by the said electromagnetic means to make operable the said switching mechanismwhereloy the said switching mechanism can operate to select any of the said signaling generators until after the connection ofthe said alternating source through the said commutator to the said switching mechanism, and a relay includecL in the circuit of the said commutator. by the operation of the said electromagnetic means operating under the control of the said commutator from the source oi? direct current tocontrol the said controlling means and the-said switching mechanism.

15. In a telephone system, the combination of an A switchboard, a B switchboard, a telephone line terminating at the B switchboard, said telephone line havinga, plurality of stations connected thereto, a link circuit at the A switchboard adapted to be connected to the trunk line,- said trunk line being adapt ed to connect at its other end to the said telephone line, a supervisory signal in the-said link circuit, a supervisory signal in the said trunk circuit,-a supervisory relay in the said trunk circuit operating under the control of the said substations sai'd supervisory relay controlling the operationofthe said supervisory signal of the link circuit, a trunk relay associated with said trunk line atthe B switchboard adapted to be operated by current from the linkcircu-it to control the operation of the trunkfline, supervisory signal and ringing circuit for thelink circuit at the A SWitchboard, a commutator included therein, said commutator adaptedto automatically operate the said trunk. relay intermittently after a ringing period, a plurality of ringing, generators, a step-by-step mechanismat the B switchboard under the control of said vtrnnkrelay to select one of said ringing generators, each of the said ringing generators being adapted to operate a particular one ,ofthe said stations on the said telephone line, the particulz'irgenerator selected and the particular station signaled depending upon-the number of operations of the saiditrunkrelay by the said commutator.

16. In a telephonesystem, the combination of a link circuit, an extension circuit therefor, a ringing generator adapted to-be associated with the said link circuit, a switch to cause such association, acommutator to interrupt the circuit of the said ringing generator and to substitute a source of direct current, switching means'to associate the said link circuit with said extension circuit, and automatic step-by-step mechanism in the said extension circuit under the control of the said commutator.

17. In a telephone system, the combination of alink circuit, an extension circuit therefor, a ringing generatormadapted to be associated with said link circuit, a switch. to causesuch association, a commutator to interrupt the circuit of the said ringing generator and to substitute a source of direct current, switching means to associate the said link circuit with the said extension circuit, automatic step-by-step mechanism in thesaid extension circuit under the control of the-said commutator, a plurality of different sources of ringing current associated with the-said extension circuit, a signaling circuit therefor,-said automatic step-by-step mechanism being adapted to associate any of the said different sources of ringing current with the said signaling circuit.

18. In a telephonesystem,the combination of a link circuit for interconnecting telephone lines, a ringing circuitfor thesaid link circuit, said-ringing circuitincluding a commutator and alternating and direct current sources, thesai'd direct current connection being intermittently broken bythe said commutator, and remotely controlled selective switching mechanism adapted to be associated-with thesaid link circuit under the control of the said commutator and the said direct currentsource.

19.111 a telephone system, a plurality of exchanges, party linesterminating in'one of said exchanges, telephone lines terminating in a second exchange, meansforextending a telephone connection from one ofsaid telephonehnes through said exchangesto a wantedparty line, a plurality ofsonrces of ringing current at-said first'mentioned exchange to selectively signal a wanted party on the selected party ;line, 1 other sources of current: ofdifi'erent character, ;.a

plurality-of impulse sending devices at: the

second exchangecooperating withsaid other sources'of current to select.ringingcurrent of the proper characteristics to signal the wanted party, and "key controlled means'to select the proper impulse sendingfdevice.

20. In-atelephone system,,-a plurality of exchanges, party lines terminating in'one of said exchanges, telephone linesterminating in asecond exchange, means'itor extending a telephone connection from one of said telephone lines through said exchanges to a wanted-party line, a plurality of sources of ringing current at said first mentioned-exchange to selectivelysignal a wantediparty on the selected party-line, othersources of current of different character, impulse sending mechanism at the-second exchange cooperating with'said othersouroes of current to select ringing current of the'proper charac teristics to signal the wanted party, and

means responsive to said impulse sending mechanism to .apply the ringing current of the selected characteristic to the selected party line.

lit)

21. In a telephone exchange system, a first exchange, a second exchange, telephone lines terminating in each exchange, a plurality of signals responsive to currents of difierent characteristics and bridged between the two sides of the telephone lines, means for interconnecting the telephone lines at said first exchange and for extending a telephone connection from any line at said first exchange to any line at said second exchange, sources of current of different characteristics at each of said exchanges to which said signals are selectively responsive, a key set at said first exchange to directly connect the sources of current at said first exchange to signals of lines tern'iinating thereon, impulse sending device at said first exchange, and means at said second exchange cooperating with said hey set and responsive to said impulse sending device and key set to select and apply current of the proper characteristic to actuate said signals.

22. In a telephone exchange system, a first exchange, a second exchange, telephone lines tern'iinating in each exchange, a plurality of signals responsive to currents of different characteristics and bridged between the two sides of the telephone lines of saithsecond ex change, means for extending a telephone connection from any line at said first exchange to any line at said second exchange, a ringing machine interrupter at said first exchange, sources of current of different characteristics at said second exchange to which said signals are selectively responsive, a key controlled impulse sending device at said first exchange including said ringing machine interrupter, and a group of relays at said second exchange variably responsive to said impulse sending device to select and L apply current of the proper characteristic to actuate a desired signal.

In Witness whereof, I hereunto subscribe my name this 31st day of July A. D. 1917.

FRANK M. SLOUGH. 

